Women who work irregular shifts have an 80 per cent higher risk of being unable to have a child, a study claims today.

There are links between women who do not work the conventional 9am-5pm day and an increased likelihood of infertility, the ESHRE global fertility conference in London heard.

The University of Southampton researchers said their results “have implications for women attempting to become pregnant, as well as their employers” if they are replicated in future studies.

However, the head of Hammersmith Hospital’s IVF unit— one of the largest in the UK — said women trying to conceive should not give up their jobs as there was no evidence this would improve their chances.

The research, which included data on 119,345 women published in studies since 1969, looked at the fertility of those working night shifts, evening shifts, split shifts and rotating shifts. Some studies have found a link between sleep deprivation caused by shift work and ill health. The new research focused on irregular menstrual cycles, fertility and miscarriage rates.

It found those working alternating shifts had a 33 per cent higher risk of irregular periods and an 80 per cent higher risk of “subfertility” — being less fertile than a normal couple.

Women who worked only night shifts did not have an increased risk of infertility but did have an increased rate of miscarriage — though the latter condition was not found in those who worked nights as part of a pattern.

Stuart Lavery, consultant gynaecologist and director of IVF Hammersmith, said: “I think it’s an important study but I would not be advising women to change their job at this stage.

“It would be a tragedy for a woman to give up a career that she loves. The most important thing you could do is timing and frequency of intercourse.

“Many people will still conceive the old-fashioned way given enough time and enough frequent intercourse.”

IVF cancer fear dismissed

FEARS that children born by IVF could be at risk of developing cancer in later life have been dismissed by London researchers.

They compared the records of 106,381 children born in the UK from 1992 to 2008 after assisted conception to the National Registry of Childhood Tumours.

The study, by the Institute of Child Health at University College London, found 108 cancers in the children born by assisted methods — which it says is “comparable” with the figure of 109.7 estimated for the general population.